Numbers 1:16-18

¹⁶These were those summoned of the assembly, princes of the tribes of their fathers, the heads of the thousands of Israel.

¹⁷And Moses and Aaron took these men who are expressed by their names,

¹⁸and gathered the whole assembly together on the first of the second month. And they declared their pedigrees after their families, according to their fathers' houses, by the number of the names, from twenty years old and upward, according to their polls.